The present invention relates to improvements in apparatus wherein an elongated web consisting of paper or other flexible material is fed lengthwise through a plurality of successive stations, especially to improvements in photographic copying machines wherein a web of photographic papaer is movable stepwise to place successive portions of a layer of photosensitive material into register with a window or opening at the copying station. More particularly, the invention relates to improvements in means for guiding the web during threading and during intermittent transport.
In certain presently known photographic copying machines, the marginal portions of a web of photographic paper extend into channels or recesses of lateral guide members. Such channels flank not only those portions of the path for the web where the web is confined from two sides but also those portions where the web is exposed, for example, the window at the copying station. A drawback of such channeled guide members is that at least one thereof must be adjusted whenever a relatively wide web is followed by a narrower web, or vice versa. The mechanism for moving one or both channeled guide members is complex, bulky and expensive, especially if it is to automatically adjust the path for satisfactory guidance of webs having different widths. Moreover, such channeled guide members cannot serve for satisfactory guidance of webs of photographic paper which are used for the making of margin-free prints. Thus, the marginal portions of such webs cannot be guided all the way through the copying machine because the printing light must reach the full width of that portion of the web which is located at the copying station.